Man, this is a deep question, one with philosophical and semi-religious connotations. Here are my beliefs.
Could someone compare jBPM with BPEL
Basically, jBPM is about defining how people and (java) systems work together. BPEL in turn defines how (web) services work together. For more details read the jBPM user guide, then the BPEL extension user guide. In particular, read section 1.6 of the latter.
What features does jBPM have that BPEL does not
Right now, jBPM features user task management, easy java code integration, free-form graphs to suit the most perverse ideas of a business analyst, and a graphical process designer. BPEL is a standard specification; it lets you wire together your web services into value-added new services.
is BPEL ok for controlling intra-organization business processes that encompass a few internal sections of the organization? Or is it more suited for inter-organization workflow management?
To be effective, BPEL needs that your organization's information systems have a service-oriented architecture already in place. In few words this means that business functions must be exposed as reusable software components. Most organizations have such an architecture in their external interfaces (i.e. those exposed to partners) but not in internal ones. You can draw your own conclusions.
Can someone explain the differences between Workflow Management, Business Process Management, and Orchestration
This is related to my first answer.
Workflow is usually understand as a procedure (flow) that is followed within an organization to achieve some objective (work) in terms of human and technology resources
BPM supersedes workflow by adding capabilities to monitor, measure, and improve (manage) the performance of an organizational procedure (business process)
Orchestration is quite a separate domain. It characterizes a group of systems and describes how they converse with each other in the long term under the perspective of each participant
BONUS CONCEPT: Choreography supersedes orchestration by providing the global perspective of interactions
Hope this serves as a basis for discussion.
i'm working on a series of blogs that explain the differences between workflow, bpm and orchestration.
keep an eye on the jboss matrix blogs